Tape recorders with reversible friction wheel drives for both reels wherein the drive motor is pivoted are well known. It has already been proposed to incline the drive motor of a record player to adjust the rotational speed of the turntable around an axis running parallel to the rotor axis. Up to now, such a design appeared to be inapplicable to projectors, since in the case of projectors, the motor is also required to drive a relatively powerful, cooling blower for the film stage, the lighting system, etc. Thus, substantially more complicated arrangements have been employed wherein the motor is rigidly connected to the apparatus and both friction discs are arranged in a shiftable manner on a gear shift. The control of these friction discs was, of necessity, a relatively high cost construction.
It was further proposed in the case of narrow film projectors to fix the drive motor in a swiveling manner around an axis running normal to the motor axis and normal to the axis of the friction discs, whereby the axis of rotation of the motor is arranged in the area of the fan baffles and the ventilator housing is arranged as a part of the projector housing.
In the case of more precise projectors, there is also the requirement of having two different rotational speeds available for the film drive with one drive motor. Up to now, electrical regulating devices have been utilized for the motor which were disliked, however, because of their small efficiency and often low rotational speed stability. Also, the use of the aforementioned fricton wheel gears with radial shifting of the friction wheel with reference to the friction discs has been considered as a possible solution. The technical results of this consideration known up to how, however, increased the already considerable and complicated construction costs.